The Grails framework is an open source web application framework built for the Groovy language. Grails not only leverages Hibernate under the covers as its persistence layer, but also implements its own object relational mapping layer for Groovy, known as GORM. With GORM, we can take a POGO class and decorate it with DSL-like settings in order to control how it is persisted. GORM can be considered a DSL as it uses many of the cool DSL features that we have discussed in previous chapters, in order to add its own mini dialect to Groovy in order to implement persistence.

Grails programmers use GORM classes as a mini language for describing the persistent objects in their application. In this section, we will do a whistle-stop tour of the features of Grails. This won't be a tutorial on building Grails applications, as the subject is too big to be covered here. Our main focus will be on how GORM implements its object model in the domain classes.